I think that you are both talking at cross purposes and are both sort of right (or wrong, whichever).
It depends if you are talking about Russian Federal Districts or any one of the historical perceptions of what constitutes "Siberia".
I was quite surprised to only find out recently that Siberia does not extend eastwards all the way to the Pacific and that the area north of Khabarovsk and east of Yakutsk, the home of the few remaining Siberian tigers, is not in fact part of geographic or political Siberia.